Ceramic Matrix Composites for Rotorcraft Engines Ceramic matrix composite (CMC) components are being developed for turbine engine applications. Compared to metallic components, the CMC components offer benefits of higher temperature capability and less cooling requirements which correlates to improved efficiency and reduced emissions. This presentation discusses a technology develop effort for overcoming challenges in fabricating a CMC vane for the high pressure turbine. The areas of technology development include small component fabrication, ceramic joining and integration, material and component testing and characterization, and design and analysis of concept components.

https://ntrs.nasa.gov/search.jsp?R=20110011258 2018-06-01T11:21:06+00:00Z

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National Aeronautics and Space Administration

www.nasa.gov

Fundamental Aeronautics Program

Michael C. HalbigTask Lead, Materials Research EngineerCeramics Branch, NASA Glenn Research Center

Subsonic Rotary Wing Project

Ceramic Matrix Composites for Rotorcraft Engines

2011 Technical ConferenceMarch 15-17, 2011Cleveland, OH

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Acknowledgements

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• Thank you to the Subsonic Rotary Wing Project and the Fundamental Aeronautics Program for their support.

• The team for the CMC Vane task includes:– Ram Bhatt, Army Research Laboratory, Cleveland, OH– Jay Singh, Ohio Aerospace Institute, Cleveland, OH– Craig Smith, Ohio Aerospace Institute, Cleveland, OH– Narottam Bansal, NASA Glenn Research Center, Cleveland, OH– Jim DiCarlo, NASA Glenn Research Center, Cleveland, OH– Martha Jaskowiak, NASA Glenn Research Center, Cleveland, OH– Jerry Lang, NASA Glenn Research Center, Cleveland, OH– Sai Raj, NASA Glenn Research Center, Cleveland, OH– Dongming Zhu, NASA Glenn Research Center, Cleveland, OH– Mike Halbig, NASA Glenn Research Center, Cleveland, OH

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Outline

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• Background Information on Ceramic Matrix Composites– Applications– Processing and properties

• Turbine Vane Application for Rotorcraft Engines

• Key Technology Development for Turbine Vanes in the SRW Project– Small component fabrication– Ceramic joining and integration– Material and component testing and characterization– Design and analysis of concept components

• Summary/Conclusions

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Applications for CMCs in Gas Turbine Engines

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Benefits:• Enabling for high OPR engines (higher turbine inlet temperatures) –reduce cooling air, reduce fuel burn and CO2 emissions• Weight = 1/3 of metals and 1/2 of titanium aluminides• High OPR engines – higher combustor temperature – increased NOX,CMC combustor liner and first stage turbine vane reduce NOX

Courtesy of GE Aircraft Engines

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Fabrication Process for Gen III SiC/SiC CMCs (2700º F Capability for G.T. Engines)

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preform

PIP CMC or CVI + PIP

CMC

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Ceramic Matrix Composite Materials- Melt Infiltrated (MI) SiC/SiC

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SiC grains and silicon within MI matrix

90° SiC fiber tow

CVI SiC

100µm

MI matrix

0° SiC fiber tow

0-90 Plain Fiber Tow Weave

Composite Cross-Section

• High thermal conductivity matrix• Elimination of interlaminar porosity• No matrix micro cracking

10 µm

BN Interphase

SylramicTM SiC fibers within a tow

SiC Fiber

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Commercial High Temperature Ceramic Material- SA-Tyrannohex (SiC Fiber Material)

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Optical Micrograph SEM Micrograph

Features• 8 Harness Satin Weave of SiCTyranno fibers• Layers hot pressed together• Hexagonal sintered fibers• Nano-layer of carbon on the fiber surface

Benefits of SiC SA-Tyrannohex• High fracture toughness• Fatigue resistance• Low weight and high temperature capability• Machinable and complex shape formation• Candidate material for the vane endcap

8 Harness Satin Fiber Tow Weave

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SRW Large Civil Tilt Rotor Mission and Requirements

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LCTR Mission: 90 passengers, range: 1000 nmi., cruise speed 300 knots, cruise alt.: 28 k-ft.

LCTR Engine Characteristics:7500-8000 HP, overall pressure ratio of 30, T4: 3000ºF hover and 2500ºF cruise, HPT turbine vane will have dimension of about 1” high and 1” long.

Engine T4 (º F) Overall Pressure RatioV22 (AE1107) 1740 16.7T700 2600 17LCTR2 (notional engine) 3000+ 30+

Comparison between the LCTR2 engine and other engines.

EIS = 2025 (2018 tech)

TOGW =108k lbm

Payload = 90 pass.

Engine = 4x7500HP

Fuel = 21,000 lbm

Range > 1,000nmi

Cruise > 300 knots

@Alt. ⇒ best range

Cruise L/D ≈ 12

Rotor tip speed

650 fps hover

350 fps cruise

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SRW Vane Task Overview

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Objective: Develop technologies for CMC turbine engine components that have higher temperature capability, higher fracture toughness, and require less cooling compared to current metallic turbine components. Targeted toward the first stage vane of the high pressure turbine (HPT). Provides higher efficiency, higher horsepower, and lower emissions. This is a technology development task rather than a component task

NASA GRC role vs. industry role: NASA GRC is focused on a cooled HPT (lower TRL) whereas industry may be more focused on less cooled and lower temperature components (higher TRL) in the low pressure turbine (LPT). GRC is focused on the engine requirements of the Large Civil Tilt Rotor Vehicle within the Subsonic Rotary Wing Project.

SRW’s CMC effort compared to CMC efforts in other NASA projects (FA and ERA): The SRW task is focused on small component fabrication and joining technology development. All CMC tasks within the projects communicate well with one another to ensure tasks are leveraged and there are no overlap in efforts.

Challenges: Fabrication of a small airfoil (1”x1”), cooling schemes, engine operating conditions (i.e. T4 > 3000F, and OPR > 30), and joining to fabricate the component.

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Current Metallic Vane Designs and Cooling Schemes

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The preference in CMC turbine component development is to insert the CMC part in-place of the metallic one(s) rather than to drastically alter the outer geometry.

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Challenges with CMC Vanes and Airfoils

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• Production challenges are in fabricating the small radii, the tapered trailing edge, integrating the endcaps, and machining cooling holes.• Design and material challenges are in meeting the high stress and high temperature requirements, providing sufficient cooling, and having a durable high temperature coating.

Tapered wall thickness at trailing edge

Coolingholes

Endcap joining

Endcap joining

Hot combustion gas

High stress and temperature

High stress

Hightemperature

Cooling channel

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Areas Being Addressed by the SRW Vane Task

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Key Technology Development for a Turbine Vane in the SRW Project

– Small component fabrication– Ceramic joining and integration– Material and component testing and

characterization– Design and analysis of concept components

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Small Component Fabrication - Objective and Concept #1

Objective: Demonstrate fabrication ability of small 1”x1” airfoils (vane cord length x height)Materials: SiC/SiC (w/Sylramic and Hi-Nicalon SiC fibers) in the form of braided CMCs, CMC/ceramic foam hybrid, SA-Tyrannohex hot pressed and machined into an airfoil shapeIssues: inter-laminar strength, leading edge, trailing edge, cooling channels, surface cooling holes

Based on T-700 metallic vane contour and possible cooling hole choices.

Two types of silicon carbide fiber will be used for fabrication (Sylramic and Hi-Nicalon-S).

The airfoils should be delivered by April.

The 6” length will be cut down and allow for multiple tests and characterization.

Planned Sub-Element Testing- Burner rig testing with and without internal cooling and EBC- Heat flux test with and without internal cooling and EBC- Testing of joined elements

CMC plug w/unidirectionalfibers

Inner CMC tube

Ceramic foam (SiC) w/ cooling channels

Cooling cavity

Outer CMC tube

Airfoil Concept #1 - Internally Cooled Vane

Endcaps will be joined to each end of the 1” long airfoil

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Small Component Fabrication- Concept #2

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Airfoil

Endcap/Ring Section

Endcap/Ring Section

Airfoil Concept #2 - Film Cooled Vane

The likely materials will be:- SiC/SiC for the airfoil- SA-Tyrannohex for the endcap

The airfoil will be fabricated this summer.

Planned Sub-Element Testing- Burner rig testing with and without internal cooling and EBC- Heat flux test with and without internal cooling and EBC- Testing of joined elements

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Ceramic Joining and Integration

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Objective: Develop ceramic to ceramic (and ceramic to metal joining technology)Materials: SiC/SiC, SA-Tyrannohex, (and superalloys)Approach: - Develop processing details:

- interlayer- conditions: time, temperature, and duration- method: diffusion bonding, brazing, etc.

- Start with ceramic to ceramic joining of simple shapes- Join more complex shapes- Characterize and test (i.e. microstructural analysis, mechanical tests, thermal cycling, and burner rig)

Joining of airfoil and endcaps

Sample

Load

Fixture

Test configuration for single lap offset shear test.

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• Ceramic substrates were ultrasonically cleaned in Acetone for 10 minutes

• Substrates were sandwiched around braze and foil layers

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• Mounted in epoxy, polished, and joints characterized using optical microscopy and scanning electron microscopy with energy dispersion spectroscopy analysis

• Atmosphere: Vacuum• Temperature: 1340ºC(10ºC above the braze liquidus temperature)• Load: 100 g/sample• Duration: 10 minutes• Cool down: 2 ºC/min

BrazingDiffusion Bonding• Atmosphere: Vacuum• Temperature: Ti 1200ºC,

Mo 1400ºC• Pressure: 30MPa• Duration: Ti 4 hr

B-Mo 4 hr• Cool down: 2 ºC/min

Applied Load

SiC

SiC

Joining Interlayer

Materials (dimensions 0.5” x 1”)- Substrate: SiC/SiC and SA-Tyrannohex- Interlayers: Ti foil (10, 20 micron)and B-Mo alloy foil (25 micron)

Materials (dimensions 0.5” x 0.5”)- Substrate: SiC/SiC and SA-Tyrannohex- Interlayer: pastes and tapes of Si-based eutectics

Ceramic Joining and Integration- Joining Processes

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Ceramic Joining and Integration - Diffusion Bonding with 10 µm Ti Foil and 25 µm B-Mo Alloy Foil

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C Si Ti1 54.28% 45.72% 0%3 44.89% 15.79% 39.33%5 0% 69.39% 30.61%

C Si B Mo O1 58.34% 41.66% 0% 0% 0%3 19.09% 5.51% 63.96% 8.25% 3.19%5 0% 0% 89.18% 10.82% 0%

Percents are atomic % Percents are atomic %

SA-Tyrannohex / Ti / SA-Tyrannohex SA-Tyrannohex / B-Mo alloy / SA-Tyrannohex

Very good quality bonds are obtained that are uniform and crack free. However, the joining process requires high applied loads and flat sub-elements for joining.

Joint

SA-TX

SA-TX

Joint

SA-TX

SA-TX

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Ceramic Joining and Integration - Joining with Si-based Eutectic Phase Paste

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Parallel SA-Tyrannohex / Si-Hf Eutectic paste / Parallel SA-Tyrannohex- Magnifications at x10, and x100

Joint

SA-TX

SA-TX

Joint Gap

SA-TX

SA-TX

• Joints from Si-Hf eutectic phase paste are good quality showing adhesion to the ceramic substrates and no microcracking or fiber delaminations.• However, joint formation is not uniform across the length and gaps are observed. Similar results were also obtained with Si-Ti and Si-Cr eutectic paste.• Processing with Si-Hf eutectic tape interlayers rather than with pastes is being pursued to provide more uniformity across the joint.

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Joining with Eutectic Phase Tapes• Three different substrates: SA-Tyrannohex

(parallel), SA-Tyrannohex (perpendicular), and MI SiC/SiC.

• Joining interlayer: Si-Hf Eutectic tape - 1 layer and 2 layers.

• 8-14 pairs were joined from each of the six sets.

• Joined with 2 mm offset for mechanical tests.

Ceramic Joining and Integration- Joining with Si-Hf Eutectic Phase Tape

SA-TX parallel, 1 layer

SA-TX perpendicular, 2 layers

MI SiC/SiC, 2 layersPreparation of SA-TX (‖) w/2 layers

Joint characterization will include optical microscopy and scanning electron microscopy (SEM) with EDS, and mechanical testing (single lap offset).

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Material and Component Characterization and Testing

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Objective: model and conduct judicious selection of materials; test materials, coated materials, airfoils, and joined sub-elements to evaluate capabilities in more relevant conditions.

Effects on SiC/SiC Rupture Strength Data in Air by Reinforcement of a CVI-MI Matrix with various High-Performance SiC Fiber Types.

Rupture Strength in Air for SiC/SiC CMC with CVI-MI, Full-PIP, and Full-CVI Matrices reinforced by Sylramic-iBN Fibers. Also Tyrannohex SA ( ).

An empirical model will be developed to act as the foundation of a more physics-based mechanistic model and predictive tool for down-selection of the optimum SiC/SiCprocesses, materials, and microstructures for a CMC HPT vane.

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Material and Component Characterization and Testing- Laser High Heat Flux Thermal Gradient Tests

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Laser High Heat Flux Thermal Gradient Rig

reflectometer 10.6 micron laser beam

cooling air

specimen

3. 5 KW CO2 High Power Laser

ceramic coating

Superalloy substrate

platinum flat coils

aluminum back plate

air gap

cooling air tube

TBC coatedback aluminum

plate edge

pyrometers

bond coat

camera

Material and Component Characterization and Testing – Ceramic Specimen Tested Under Cyclic Heat Flux Thermal Gradients

SA Tyrannohex initially selected for SRW project baseline airfoil material for evaluation: 1” square plate specimen

Specimen under testing0

200

400

600

800

1000

1200

1400

1600

0 50 100 150 200

Tsurface, °CTback, °C

Tem

pera

ture

, °C

Time, hours

Reduced cooling

• SA Tyrannohex ceramic selected as a candidate material due to its excellent high temperature mechanical and thermal properties.• The first 25x25x10 mm specimen was tested at under turbine thermal gradient cycling conditions: Tsurface 2300-2400ºF (1260-1316ºC), Tback 1700-1750ºF (927-954ºC), 1 hr cyclic in air, for total 195 cycles• Late stage testing (after ~110 cycles) showed specimen delamination (increased surface temperature and reduced back temperature with cycling under heat flux)

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Material and Component Characterization and Testing - High Temperature Biaxial Creep Tests

High temperature biaxial creep tests is an ideal testing capability for SRW coating and CMC airfoil development.

Cooling shower head jets

specimen

Ball-on-Ring fixture

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

-500

0

500

1000

1500

0 5 10 15 20 25

Creep displacement

Load, N

Dis

plac

emen

t, m

m

Load

, N

Time, hours

High temperature biaxial creep tests rig.

FEM analysis of a coated disk.

Creep response at 454 N constant loading 23

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Material and Component Characterization and Testing- High Velocity High Pressure Burner Rig

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High Velocity High Pressure Burner Rig Recession Tests

6 atm, tested at 2500ºF specimen surface, 200m/s gas velocity

3x1/2” bar specimen set up

Uncoated SA Tyrannohex Ceramic Specimen High Pressure Burner Rig

Recession Tests – 200 m/s

0.0

0.5

1.0

1.5

2.0

0 5 10 15 20

Specimen #7 weight loss, mg/cm2-hSpecimen #8 weight loss, mg/cm2-h

Spec

imen

#7

wei

ght l

oss,

mg/

cm2-

h

Total accumulated time, hr

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Design and Analysis of Concept Components

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Objective: Investigate design issues for a vane component with emphasis on thermal and mechanical conditionals, material capabilities, and component cooling.

Approach: - In-house: stress analysis on first generation airfoils- Out-of-house: N&R Engineering Phase 1 and Phase 2 SBIRs.

Blade Stress Analysis for Determination of a Blade versus Vane Task.

Vane Temperature Distribution (N&R).

Vane Pressure Loads (N&R).

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Design and Analysis of Concept Components- Thermal and Stress Analysis of Vane Designs

Airfoil Concept #1 - Internally Cooled Vane

Airfoil Concept #2- Film Cooled Vane

Additional Design for Internally Cooled Vane

For the above designs, thermal profiles and loads due to thermal and mechanical stresses will be calculated.

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Summary/Conclusions

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• CMCs in turbine engine applications offer such benefits as:- Reduced fuel burn, reduced emissions, and lower weight- Higher temperature capability enables engine operation at higher power density

(higher temperature and pressure)- Reduced cooling results in improved efficiency

• The SRW Vane task is addressing unique challenges the for the LCTR mission and engine class.

• Progress is being made in critical areas to include:• Small component fabrication• Ceramic joining and integration• Material and component testing and characterization• Design and analysis of concept components

• The concept sub-components and components with features for study will be demonstrated in challenging conditions that are relevant to the engine conditions.

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